The present invention relates to reclosable thermoplastic bags and to the mechanisms employed for closing such bags. More particularly, the invention relates to reclosable thermoplastic bags having zipper-type closures.
Reclosable thermoplastic bags with zipper-type closures have come into widespread use. The problem addressed by the present invention pertains to the determination or perception of whether or not the zipper of a reclosable plastic bag is properly closed or "zipped". Such a determination is often difficult save with a close visual inspection of the zipper.
One known way of making the determination easier is to use a zipper which provides a color change when the zipper is properly zipped. Different colors are utilized in each of the opposing zipper profiles to produce a third distinct color when the profiles are interlocked. Zippers utilizing such a color change are seen in U.S. Pat. Nos. 4,186,786 and 4,285,105. One disadvantage of using such a color change is that it may occur when the opposing zipper profiles are closely overlapped instead of only when the profiles are properly interlocked.
Commonly-assigned copending U.S. Ser. No. 07/531,951, filed on Jun. 1, 1990, solves the aforementioned problem and overcomes the deficiencies of the known art by providing a zipper for a reclosable thermoplastic bag that closes with a vibratory or bumpy feel and/or produces an audible clicking sound along its length when being closed, so that the fact of closure can be confirmed preferably both by sound and feel in addition to, or to the exclusion of, the close visual inspection required with previous zipper structures. Several embodiments of suitable zippers are described, with each of the embodiments having a part of a rib or groove profile which is structurally discontinuous in some fashion along its length.